1. Field of the Invention
The present invention relate to a process for preparing a 2-alkyl-3-aminothiophene derivative useful as an agricultural fungicide or intermediate thereof, and novel 3-aminothiophene derivatives.
2. Description of the Related Art
Japanese Patent Application Laid-Open (JP-A) No. 9-235282 (EP-A 0737682 A1) describes that a certain kind of 2-alkyl-3-aminothiophene derivative has strong control effect against various plant disease damages. For producing this 2-alkyl-3-aminothiophene derivative, there is envisaged a method in which an alkyl group is directly introduced into 2-position of a 3-aminothiophene derivative. For example, Tetrahedron Letters, 34, 5715 to 5718 (1993) teaches that 2-alkyl-3-aminothiophene is obtained by reacting 3-aminothiophene with various aldehydes in the presence of p-toluenesulfonic acid and selenophenol. ##STR2##
(wherein, R' represents an alkyl group.) PA1 wherein, R represents a hydrogen atom, alkyl group or alkoxy group which may be substituted, aromatic or non-aromatic hydrocarbon ring which may be substituted, aromatic or non-aromatic heterocyclic ring which may be substituted, each of R.sup.1, R.sup.2, R.sup.3 and R.sup.4 independently represents a hydrogen atom or straight or branched alkyl group having 1 to 12 carbon atoms, and R.sup.1 and R.sup.2, R.sup.3 and R.sup.4, R.sup.1 and R.sup.3, R.sup.1 and R.sup.4, R.sup.2 and R.sup.3 or R.sup.2 and R.sup.4 may together form a cycloalkyl group, comprising reacting a compound represented by the formula (2): ##STR4## PA1 wherein, R is as defined above, with a compound represented by the formula (3): ##STR5## PA1 wherein, R represents a hydrogen atom, alkyl group or alkoxy group which may be substituted, aromatic or non-aromatic hydrocarbon ring which may be substituted, aromatic or non-aromatic heterocyclic ring which may be substituted, each of R.sup.1a, R.sup.2a, R.sup.3a and R.sup.4a independently represents a hydrogen atom, straight or branched alkyl group having 1 to 12 carbon atoms or straight or branched alkenyl group having 1 to 12 carbon atoms and R.sup.1a and R.sup.2a, R.sup.3a and R.sup.4a, R.sup.1a and R.sup.3a, R.sup.1a and R.sup.4a, R.sup.2a and R.sup.3a or R.sup.2a and R.sup.4a may together form a cycloalkyl group or cycloalkenyl group, comprising reacting a compound represented by the formula (2): ##STR7## PA1 wherein, R is as defined above, with a compound represented by the formula (3): ##STR8## PA1 wherein, R.sup.a represents a group represented by any of the following (A1) to (A12): ##STR10## PA1 wherein, R, R.sup.1, R.sup.2, R.sup.3 and R.sup.4 are as defined above, further hydrolyzing the resultant compound under acidic or alkaline condition to obtain a compound represented by the formula (5): ##STR14## PA1 wherein, R.sup.1, R.sup.2, R.sup.3 and R.sup.4 are as defined above, and reacting this compound with a compound represented by the formula (8a): ##STR15## PA1 wherein, R.sup.9 represents a hydrogen atom, carboxyl group or alkoxycarbonyl group having 1 to 6 carbon atoms and R.sup.a represents a group represented by any of the following (A1) to (A12): ##STR17## PA1 wherein, R.sup.b represents a hydrogen atom, alkyl group or alkoxy group which may be substituted, aromatic or non-aromatic hydrocarbon ring which may be substituted or aromatic or non-aromatic heterocyclic ring which may be substituted, and each of R.sup.1a, R.sup.2a, R.sup.3a and R.sup.4a independently represents a hydrogen atom, straight or branched alkyl group having 1 to 12 carbon atoms or straight or branched alkenyl group having 1 to 12 carbon atoms, and R.sup.1a and R.sup.2a, R.sup.3a and R.sup.4a, R.sup.1a and R.sup.3a, R.sup.1a and R.sup.4a, R.sup.2a and R.sup.3a or R.sup.2a and R.sup.4a may together form a cycloalkyl group or cycloalkenyl group, excepting the case in which R.sup.b represents a group represented by any of the following (A1) to (A12): ##STR19## PA1 wherein, R, R.sup.1a to R.sup.4a are as defined above. PA1 wherein, R.sup.b represents a hydrogen atom, alkyl group or alkoxy group which may be substituted, aromatic or non-aromatic hydrocarbon ring which may be substituted or aromatic or non-aromatic heterocyclic ring which may be substituted, and each of R.sup.1a, R.sup.2a, R.sup.3a and R.sup.4a independently represents a hydrogen atom, straight or branched alkyl group having 1 to 12 carbon atoms or straight or branched alkenyl group having 1 to 12 carbon atoms, and R.sup.1a and R.sup.2a, R.sup.3a and R.sup.4a, R.sup.1a and R.sup.3a, R.sup.1a and R.sup.4a, R.sup.2a and R.sup.3a or R.sup.2a and R.sup.4a may together form a cycloalkyl group, excepting the case in which R represents a group represented by any of the following (A1) to (A12): ##STR24## PA1 wherein R represents a hydrogen atom, alkyl group or alkoxy group which may be substituted, aromatic or non-aromatic hydrocarbon ring which may be substituted, aromatic or non-aromatic heterocyclic ring which may be substituted, each of R.sup.1, R.sup.2, R.sup.3 and R.sup.4 independently represents a hydrogen atom or straight or branched alkyl group having 1 to 12 carbon atoms, and R.sup.1 and R.sup.2, R.sup.3 and R.sup.4, R.sup.1 and R.sup.3, R.sup.1 and R.sup.4, R.sup.2 and R.sup.3 or R.sup.2 and R.sup.4 may together form a cycloalkyl group, each of R.sup.1a, R.sup.2a, R.sup.3a and R.sup.4a independently represents a hydrogen atom, straight or branched alkyl group having 1 to 12 carbon atoms or straight or branched alkenyl group having 1 to 12 carbon atoms, and R.sup.1a and R.sup.2a, R.sup.3a and R.sup.4a, R.sup.1a and R.sup.3a, R.sup.1a and R.sup.4a, R.sup.2a and R.sup.3a or R.sup.2a and R.sup.4a may together form a cycloalkyl group or cycloalkenyl group. PA1 wherein R.sup.b represents a hydrogen atom, alkyl group or alkoxy group which may be substituted, aromatic or non-aromatic hydrocarbon ring which may be substituted or aromatic or non-aromatic heterocyclic ring which may be substituted. Each of R.sup.1, R.sup.2, R.sup.3 and R.sup.4 independently represents a hydrogen atom or straight or branched alkyl group having 1 to 12 carbon atoms, and R.sup.1 and R.sup.2, R.sup.3 and R.sup.4, R.sup.1 and R.sup.3, R.sup.1 and R.sup.4, R.sup.2 and R.sup.3 or R.sup.2 and R.sup.4 may together form a cycloalkyl group, excepting the case in which R.sup.b represents a group represented by any of the following (A1) to (A12): ##STR27## PA1 wherein R.sup.9 represents a hydrogen atom, carboxyl group or alkoxycarbonyl group having 1 to 6 carbon atoms, R represents a hydrogen atom, alkyl group or alkoxy group which may be substituted, aromatic or non-aromatic hydrocarbon ring which may be substituted or aromatic or non-aromatic heterocyclic ring which may be substituted, which is an intermediate in the present invention will be described. PA1 wherein R is as defined above, the formula (9) means the case in which R.sup.9 in the formula (6) is an alkoxycarbonyl group having 1 to 6 carbon atoms, the formula (10) means the case in which R.sup.9 in the formula (6) is a carboxyl group, the formula (2) means the case in which R.sup.9 in the formula (6) is a hydrogen atom, and R.sup.10 represents an alkyl group having 1 to 6 carbon atoms. Examples of the alkyl group represented by R.sup.10 include alkyl groups having 1 to 6 carbon atoms such as a methyl group, ethyl group, propyl group, isopropyl group, butyl group, tert-butyl group, hexyl group and the like. PA1 wherein R.sup.9 represents a hydrogen atom, carboxyl group or alkoxycarbonyl group having 1 to 6 carbon atoms, and R.sup.a represents a group represented by any of the following (A1) to (A12): ##STR31## PA1 wherein R represents a hydrogen atom, alkyl group or alkoxy group which may be substituted, aromatic or non-aromatic hydrocarbon ring which may be substituted, aromatic or non-aromatic heterocyclic ring which may be substituted, each of R.sup.1, R.sup.2, R.sup.3 and R.sup.4 independently represents a hydrogen atom or straight or branched alkyl group having 1 to 12 carbon atoms, and R.sup.1 and R.sup.2, R.sup.3 and R.sup.4, R.sup.1 and R.sup.3, R.sup.1 and R.sup.4, R.sup.2 and R.sup.3 or R.sup.2 and R.sup.4 may together form a cycloalkyl group. PA1 wherein R.sup.1 to R.sup.4, R.sup.a are as defined above.
However, in this literature, there is utterly no description in which 2-alkyl-3-aminothiophene having a secondary alkyl group is synthesized. For obtaining a 2-alkyl-3-aminothiophene derivative having a secondary alkyl group using a synthesis method described in this literature, 3-aminothiophene derivative has to be reacted with ketones. However, when the present inventors substituted an aldehyde for the ketone and conducted this reaction, 3-aminothiophene was decomposed and the intended 2-alkyl-3-aminothiophene derivative or 2-alkenyl-3-aminothiophene derivative could not be obtained (Reference Example 1). Further, this literature includes a problem as an industrial production method since the reaction uses as a reducing agent selenophenol which is not easily obtained industrially.
Further, Tetrahedron 54, 9055 to 9066 (1998) teaches that when an aldehyde having branching at .alpha.-position is reacted with 3-aminothiophene or 3-aminothiophene derivative, an primary alkenyl group is introduced. However, this literature includes utterly no description regarding reactions using a ketone.